During diagnosis your prostate cancer may be assigned a stage. These stages are determined by a variety of information, including imaging results, prostate biopsy reports, PSA levels, and more. Prostate cancer is generally assigned a stage from I to IV (1 to 4), with I being less advanced and IV being more advanced. There are two types of staging that can be used to characterize your cancer, clinical and pathologic. Clinical staging involves making predictions on your cancer only using diagnostic tests including your digital rectal exam, biopsy, images, and other lab tests. Pathologic staging is based on the clinical staging, in addition to staging performed during or after surgery for prostate cancer, and is often more accurate since your surgeon is able to get a first-person view of what’s going on.
TNM system
In order to determine your stage, you will be assigned into different TNM categories. TNM categories were created by the American Joint Committee on Cancer (AJCC). These categories classify your case of prostate cancer based on the extent of the primary tumor found (T category), whether or not your cancer has spread to local lymph nodes (N category), and whether or not your cancer has spread to different parts of your body, also known as metastasis (M category). Within each category, there is a set of potential cancer characteristics. Whichever characteristics your cancer most matches will be the value you are assigned. These sub-categories include the following:
T category
The T category is broken into T1-T4 and describes the primary tumor site in the prostate.
- T1: Your prostate cancer is not visible on imaging screens, nor felt during a digital rectal exam. These types of prostate cancer are typically found by accident during another procedure, such as a transurethral resection of the prostate (TURP) for another condition such as BPH (the non-cancerous growth of the prostate). If prostate cancer makes up less than 5% of the tissue removed during TURP, the cancer is classified as T1a. If the cancer is more than 5%, it is considered T1b. If your prostate cancer was found during a needle biopsy that was performed because you had an increased PSA level, the cancer is considered T1c.
- T2: Your cancer is visible on imaging tests and can be felt during a digital rectal exam, but it appears to have not expanded beyond the prostate. If your cancer is only on one side of the prostate and takes up less than half of that side, it is called T2a. If the cancer is on one side only and takes up more than half of that side, it is considered T2b. If your cancer is on both sides of the prostate, it is considered T2c.
- T3: Your cancer has begun to spread beyond the prostate. If the cancer has not reached the seminal vesicles it is classified as T3a, and if it has reached into the seminal vesicles, it is considered T3b.
- T4: Your cancer has spread into other tissues next to the prostate (besides the seminal vesicles), including the rectum, bladder, or pelvic wall.
N category
The N category assesses if the cancer has spread to local lymph nodes, and is broken into NX, N0, and N1.
- NX: Your local lymph nodes were not assessed and it is unknown if there is cancer in the lymph nodes.
- N0: Your cancer has not spread into any local lymph nodes.
- N1: Your cancer has spread into one or more local lymph nodes.
M category
The M category describes the metastasis (or spread) of cancer to distant locations in the body. This happens in advanced cancer cases, and is broken down into MX, M0, and M1.
- MX: Distant metastases were not assessed and it is unknown if there is cancer in distant organs.
- M0: Your cancer has not spread beyond the local lymph nodes.
- M1: The cancer has spread beyond the local lymph nodes. If it has spread to lymph nodes outside of the pelvis, the cancer is classified as M1a. If the cancer has spread to the bones it is considered M1b. If the cancer has spread to other organs, with or without bone involvement, including the liver, brain, or lungs, it is considered M1c.
Stages I-IV
After classifying your prostate cancer into the appropriate TNM categories, you will be assigned a stage. Each stage has a specific set of TNM values associated with it, but can be influenced by other results such as your PSA levels or Gleason score. The general description of each stage is as follows:
- Stage I: The cancer is generally in the prostate only and is slow-growing. Individuals in stage I typically have no cancer in the local lymph nodes and have a Gleason score of 6 or less, and a PSA less than 10.
- Stage II: Stage II is broken into two categories, IIA and IIB. In both classes, the cancer is still usually found in the prostate only, but the cancer cells may be growing faster or look more abnormal. Distinguishing whether or not a cancer is stage IIA or IIB may come from the individual’s PSA test or Gleason score, with higher values of these falling into the IIB group.
- Stage III: In stage III the cancer typically has spread beyond the prostate gland and is now in other structures or tissues around the prostate gland. The local lymph nodes still do not have cancer.
- Stage IV: By stage IV, the cancer has made it to the local lymph nodes and has potentially metastasized to other parts of the body.
Overall, the classification and staging of prostate cancer can be a very confusing and overwhelming process. Your doctor will let you know what stage you are in, and can show you the information they used to determine why you fall into a certain category or stage group.1-3